Circuit interrupting apparatus



April 414, 1942. v G. F. McMAHON CIRCUIT INTERRUPTING APPARATUS 4 Sheets-Sheet 1 Filed June 14, 1940 w 0/0 H s e fiMc/EZa/zm I 4 Geo p a. F. MCMAHON 2,279,631

CIRCUIT INTERRUPTING APPARATUS Filed June 14, 1940 4 Sheets-Sheet 2 f 33 w. 4g 0 29 Q v 1 V 5 Z9 SI 8 w 51- 2 2;

70 W l g ao ye F/VCMQ/ZO/Z P! 14, 1942p a. F. M MAHON ,2 9,631

CIRCUIT INTERRUPTING APPARATUS Filed June 14, 1940 4 Sheets-Sheet 3 April 14, 1942- a. F. M MAHON 2,279,631

' CIRCUIT'INTERRUPTJNGAPPARATUS Filed June 14, 1940 4 Sheets-Sheet 4 MA G VEUC 8/ x ['2U6fli'07:

GeoryeFMc/Vahm Patented: Apr. 14,1942

CIRCUIT INTEBRUPTING APPARATUS George F. McMahon, Chicago, Ill., assignor to porationof Delaware Schweltser a Conrad, Inc., Chicago, lll., a cor- Application June 14, 1940, Serial No. 340,423

2'; Claims. 101. 200-120) This invention relates, generally, to circuit interrupters and it has particular relation to the prevention of the expulsion of combustible material from a circuit interrupter on operation there- When an arc is'formed between a pair of terminals connected to a suitable source of electrical energy, a certain amount of metal is vaporized and new metallic compounds are formed as the result of chemical combination of the surrounding air or are extinguishing materials. The origin of this metal is the terminals themselves, or, if they are connected by metallic fusible means, then the vaporized metal comes from both the terminals and the fusible means. The arc' extinguishing chemicals are generally in close proximity to the fusible means and terminals and they are vaporized and decomposed by the heat of the arc.

In the normal state at room temperature the metal which is vaporized by the heat of the arc is usually considered as being nonmagnetic.

- Often the magnetic susceptibility of some metals .changes upon vaporization due to increase in temperature,-an increase .being noted in some special cases as with silver. In the newly formed metallic compounds the magnetic susceptibility of some is sometimes greater than that of the original pure metal vapor. Ordinarily the terminals are formed of copper, aluminum or brass.

If the terminals are connected by fusible means, it usually takes the form of silver, tin, lead, zinc or alloys thereof. At the temperature of the arc, the vaporized metal takes the form of ionized metallic particles or metallic compounds and it has been found that they possess magnetic properties and that their positions can be influenced or controlled by a strong magnetic field. In order to extinguish the are between theterminals resort is had to various means. The terminals can be relatively moved apart so as to extend the are so far that it cannot maintain itself. Arc extinguishing materials in either the liquid or the solid form or both are so positioned relativelyto the arc that an arc extinguishing medium in the form of gas or vapor is evolved therefrom by the heat of the are which assists in extinguishing the same. Gas, such as air, under pressure may be blown across the arc to extinguish it. Combinations of these means are also employed. Generally a blast results which sweeps out the space between the terminals so as to prevent restriking of the arc once it has been extinguished. 1 The blast whichresults from the sweeping out action of course contains the metallic particles as well as the arc extinguishing medium, newly formed compounds, and other gases. It is customary, in the event that relatively high pressure results from the are blast, to exhaust it to the atmosphere. As soon as the particles are exposed to the air, they support combustion and a flame is the immediate result as oxidation progresses. Such a flame is often observed in the products of the are that form the blast when 'the latter encounters the air, even after the arc between the terminals itself has been extinguished. Thus, after the circuit has been satisfactorily interrupted, there is still the possibility, and it often happens, that a quantity of flame will appear outside of the circuit interrupter in the cloud of other materials making up the arc blast.

Flame, since it contains ionized or electrically charged particles, is a good conductor of electricity. If it comes into proximity with a high voltage circuit, it may either cause it to be grounded, or to be short circuited on another conductor. It is to the prevention of such a flame that the present invention is directed.

An object of this invention is to prevent the occurrence of a flame in the arc blast outside of a circuit interrupter. 1

Another object of this invention is to remove from the arc blast particles that support combustion on exposure to the air.

A further object of this invention is to remove the particlesfrom the arc blast by magnetic means.

It is also an, object of this invention to sweep out the space between a pair of terminals between which an arc is formed by a blast which carries with it ionized and unionized particles, to'confine the blast during a portion of its travel and whilethus confined to remove or influence the otherwise normal path" of travel of the particles contained therein so that they are not permitted to contact the air.

Another object of the invention is to influence the path of travel'of the particles by magnetic means while the blast is confined under pressure.

Other objects of this invention will, in part, be obvious and in part appear hereinafter.

For a more complete understanding of the nature and scope of this invention, reference may be had to the following detailed description taken in connection with the accompanying drawings, in which: Figure 1 is a longitudinal sectional view of one embodiment of the invention, the upper and lowment of the invention;

Figure 4 is a detail sectional view taken along the line H of Figure 3A;

Figure 5 is a perspective view of the permanent magnets and holder therefor that are employed in the embodiments of the invention shown in Figures 3A and 3B;

Figure 6 is a longitudinal sectional view of still another embodiment of the inventionnand Figure 7 is a detail sectional view taken along the line 'I'I of Figure 6.

Referring now particularly to Figure 1 of the drawings, it will be observed that the reference character l designates, generally, a liquid'type fuse device such as is shown in Conrad Patent No. 2,091,430. It is provided with a tubular insulating housing II that is preferably formed of glass and is filled with a liquid i2 to the level indicated at 13. The liquid l2 may be as disclosed in McMahon Patent No. 2,077,429. In general it comprises a halogenated hydrocarbon. In particular it may comprise a chlorinated hydrocarbon.

separable terminals I4 and IS, the terminal I being stationarily mounted, as will hereinafter appear, and the terminal I being arranged to be moved away from the stationary terminal M in order to elongate the are formed therebetween to extinguish the same as will be readily understood. The terminals M and [5 are interconnected by a fusible element l6, preferably in the form of silver wire and by a strain element l1 comprising a high strength wire such as a nickel chromium alloy wire. Around the fusible and arcing chamber l8, of insulating material through which the liquid I2 is forced to flow by means of a liquid director I9 that is carried by the movable terminal IS. The terminal l5 carrying the liquid director I9 is arranged to be retracted by a coil tension spring when thefusible and strain elements [6 and I1 blhw. The terminal I5 is connected by means of flexible conductors 2| to a terminal, not shown, at the lower end of the housing or fuse tube l I. y

The arcing chamber I8 is centrally mounted in the upper end of the housing II by means of an insulating washer 24 that is threaded, as shown,

into a metallic terminal 25 that is secured to the a metallic spider 21 which supports the stationary terminal M in operative position.

It will be observed that the terminal 25 is provided with a cylindrical extension 28 that is closed at its upper end by a vent cap 29, which is arranged to be blown off in the event that sufflcient pressure is developed within the extension 28 on operation of the fuse device I0. When a dry type of fuse, suchas shown in Triplett Patout No. 2,183,728,v is used, it is not necessary to seal the fuse housing.

' The fusible element I6 is arranged to melt on flow of predetermined current therethrough, such as on the occurrence of an overload or short circuit in the circuit in which the fuse device I0 is connected. As soon as the fusible element IS The fuse device It is provided with a pair of melts all of the current flow is transferred to the strain element. I! which promptly parts and permits the terminal l5 to be retracted by the spring 20. An arc is formed between the terminals I4 and I5 which it is desired to extinguish as promptly as possible. This is accomplished, as

is now well known, by elongating the arc and at the same time permitting the heat of the arc to evolve an arc extinguishing medium from an arc extinguishing material to sweep out the arc space so that at current zero on an alternating current circuit the arc space will be substantially nonconducting and the arc will not restrike.

In the embodiment of the invention disclosed in Figure 1 of the drawings, the arc extinguishing material comprises the liquid. l2 which is directed into the arc space between the terminals I4 and I5 by the liquid director I9. Due to the heat of the arc the liquid is vaporized and it 40 strain elements I8 and I1 there is provided an:

sweeps out the arc space within the arcing chamber l8. This is effective in promptly extinguishing the arc and preventing further current flow. This action results in a blast being created which flows outwardly through the upper end of the arcing chamber l8 along the paths indicated by the arrows 30 through openings 3| in the spider 21, and up into the extension 28. Now this blast comprises not only the gasified arc extinguishing liquid or the arc extinguishing medium in gaseous form but also is contains metallic and non-metallic particles and compounds of the same which are formed as a result of the volatilization of the arc extinguishing liquid l2, fusible element l6, strain element I1 and portions of the terminals l4 and I5 which are subjected to the direct heat of the arc.

' If th blast containing these ionized particles is discharged into the air, a flame results therein due to the oxidation of the particles which support combustion. While the remaining part of the blast is relatively harmless in so far as its electrical characteristics are concerned, this is 7 not the case with the flame. As is well known,

such a flame constitutes an electrical conductor and, as indicated hereinbefore, if it comes into" between them; In a complicated switching structure it is sometimes extremely diflicult to provide sufficient free space abov the fuse devices so that any flame which is emitted therefrom cannot possibly cause these undesired results. Consequently, it is desirable to provide some means for preventing the formation of this flame.

In order to accomplish this desired end, advantage is taken of the fact that the particles which are contained in the blast are magnetic or possess magnetic properties or can be influenced or attracted by a magnetic field when they are about the temperature of th arc. To provide the magnetic field permanent magnets 32, 33, and, which, as shown in Figure 2, are of a horseshoe shape, are located in spaced apart relation by spacers 35 and 36 within the cylindrical extension 28. The blast resulting from the -a,a7a,os1- thereof when the resulting blast generates sufficient pressure within the extension 29 so as to blow the cap 29 oil, substantially all of the ionized particles therein are removed therefrom by the permanentm snets 92, II and" 94 so that the remaining unionized constituents of the blast are incapable of producing a flame when they encounter the air.

It will be noted that permanent magnet 39 is positioned oppositely of the permanent magnets 32 and 94. This is to Provide a somewhat more balanced design. Instead of this arrangement, the permanent magnets 92, ll and 94 may occupy other relative positions as may be'desired, a suflicient number being providedin order to insure removal or displacementv When the fusible and strain elements 4 and II are blown on the occurrence of an overload,

an arc is formed between the terminals 49 and 49 and the latter terminal is released for movement through the bore ll under the influence of the coil spring II. An are medium, fluorine, if lithium fluoride is used for the solid arc extingnishing material II, is evolved from the wall of the bore 68 due to the heat of the arc and a blast is formed for sweeping out the arc space between the terminals 49 and 49. Ordinarily the arc will be extinguished long before i the rod-like terminal 49 reaches the lower end of of the maximum quantity of ionized particles 40 designates, generally, a combination of solid.

material and liquid fuse device of the type disclosed in the copending application of McMahon, Serial No. 239,263, filed November 7, 1938.- This circuit interrupter or fuse device comprises a fuse tube or housing 4i, preferably formed of glass, having corrugations 42 at its upper end for improving the electrical insulating properties 1 thereof. At its lower end it-is provided with a terminal 43 which is sealed in place by conventional means. The housing 4| is fllled with a liquid 44, which is of the same character as the liquid i2 described hereinbefore, to the level indicated at 45.

The arc in the fuse device 40 is arranged to be drawn between a stationary terminal 46 that is carried by a metallic bridge 41 that is supported in a terminal 49 sealed to th upper end of the housing 4| and a relatively movable redlike terminal 49, the lower end of which is secured in a spring and cable fastener 59. A coil tension spring ii and a flexible conductor 52 are secured, as shown, to the spring and cable fastener 59 at their upper ends and at their lower ends they are secured to a similar spring and cable fastener 53 which is fastened to the lower terminal 49. It will be understood that the spring 5i serves to retract the rod-like terminal 49 and that the flexible conductor 52 serves to provide a low ce current path between the rod-like terminal 49 and the terminal 43.

The terminals 49 and 49 are interconnected by a fusible element 84 which may be formed of silver and a strain element I which may be formed of a high strength alloy such as a nickel chromium alloy.

The rod-like terminal 49 is mounted for movement within a bore 59 in a mass of solid are extinguishing material I! that is arranged in the form of ring-like sections. It has been indicated in the application of McMahon that the solid arc ends: the housing 4|.

the bore 59. The arrangement is such that the upper end of the rod-like terminal 49 will be drawn below the liquid level 48 so that an excellent dielectric is provid between the terminals 49 and 49 after the arc been extinguished.

The upper end of the bore II opens into a throat or outflared opening 92 in a ring 43 of suitable insulating material. It is within the throat 62 and upper end of the bore N that the are between the terminals 46 and 49 is formed on blowing of the fusible and strain elements I4 and As a result or the heat of the are a blast is created for sweeping out the arc space between ill the terminals 46 and 49 in order to extinguish the arc. This blast is formed by the arc extinguishing medium, that is evolved due to the heat of the are from the solid arc extinguishing material 59. As before described, the blast that has swept out the arc space between the terminals 49 and 49 carries with it a quantity of metallic particles resulting from the volatilization' of the fusible and strain elements 54 and SI and portions of the terminals 48 and 49. If the'blast with these metallic particles is discharged into the air, a conducting flame would be formed which is undesirable forthe reasons set forth hereinbefore.

Again advantage is taken of the magnetic characteristics of the electrically charged particles in the blast in order to remove them from the same. It will be observed that the terminal 48 is provided with a cylindrical extension '4 that is closed at its upper end by a cap nut 69 and a vent cap 66, which is arranged to be blown off in the event that suflicient pressure is developed within the extension 64.

Mounted on the support member 6| is a magnet manent magnets 69 are clearly shown in Figures 4 and 5 of the drawings.

The arrangement of the permanent magnets 99 is such that the passage of the blast through the cylindrical extension 64 is substantially unhindered. The permanent magnets 69 may be formed as hereinbefore described for the permanent magnets 32, 33 and 34. The magnets 99 are preferably arranged with opposite poles facing each other so that the lines of force. are substantially perpendicular to the normal path of the exhaust gases passing through the chamber 94. In order to insure the effectiveness of the permanent magnets 99,- all of the adjacent parts are formed of non-magnetic material suchas brass or copper.

1. The magnets, were covered with a heavy de- 7 posit'of carbon, finely divided metal and metallic chlorides.

2. The surfaces of walls in the chamber containing the magnets showed a white deposit consisting of metallic chlorides and underneath that a deposit of carbon, indicating that a selective action had occurred as the products of the arc were influenced by the magnetic field. Zinc chloride was one of the metallic chlorides found in a fairly large quantity. The zinc, derived from the brass forming the terminals combined with chlorine from the arc extinguishing liquid I! to form the zinc chloride which, at the high temperature due to the heat of the arc, was strongly influenced by the magentic field. The presence of carbon is due to the decomposition of this same are extinguishing material. I

In Figures 6 and '7 of the drawings another embodiment of the invention is shown. As there illustrated the reference character," designates, generally, a circuit interrupter that is generally similar to the circuit interrupter 40 described hereinbefore and illustrated in Figures 3A and 3B of the drawings. The circuit interrupter or fuse device 14 is provided with an insulating tube or housing 15 within which an-arc is adapted to be formed between a stationary terminal I6 carried by a spider TI on an upper terminal 18 and a relatively movable rod-like terminal I9 that is disposed for longitudinal movement within a bore 80 in a mass of solid arc extinguishing material 8| arranged in ring-like sections. The solid arc extinguishing material 8| is carried by means of a suitable tube or sleeve 82 which is supported by a support member 83 that is carried by the terminal 18. The terminals 16 and 19 are interconnected by a fusible element 84, preferably in the form of a silver wire anda strain element 85 that is preferably formed of high strength alloy wire, .such as nickel chromium wire.

The creation of the blast for sweeping out the arc space between the terminals 18 and I! in the fuse device T4 is substantially the same as previously described for the fuse device 40, shown in Figures 3A and 3B of the drawings. This blast will contain metallic particles which will support combustion on contact with the air and cause a conducting flame to be established which is undesirable for the reasons previously set forth.

The terminal I8 is provided with an integrally formed cylindrical extension 88 that is closed at its upper end by a cap nut 81 and a vent cap 88 that is arranged to be blown off when willcient pressure is generated within the extension 88. The blast resulting from the circuit interruption and the are formed between the terminals I6 and I9 flows upwardly along the paths indicated by the arrows 89 through openings 80 in the spider 11. It willbe observed that, in the specific embodiment disclosed, four openings shaped permanent magnets 8| are provided immediately above the spider l1 and are so arranged that their ends project somewhat over the respective apertures 80, as is more clearly shown in Figure 7 of the drawings. then created across the paths 88 of the blast and it is effective, asprevlously described, to attract or influence the particles which, at the temperature of the blast, possess magnetic properties.

It will be noted that several sets of arcuateLv shaped permanent magnets 9| are provided, the sets being positioned one above the other and spaced apart by spacer rings 92. The permanent magnets 91 making up the set immediately above the spider l1 and making up the set which constitutes the third set from the bottom are aligned. The permanent magnets 8| making up the remaining two sets are aligned but are shifted about 45 with respect to the other two sets in order to overlap the paths 89 of the blast as directed through der l1.

In order to concentrate the magnetic fields of the permanent magnets H all of the parts associated therewith are formed of suitable relatively nonmagnetic material such as copper or brass.

In all of the embodiments of the invention dis- I closed, the arc will usually be extinguished by the time that the blast reaches the atmosphere. The only magnetic field that is present after the arc is extinguished then is that which is provided by the permanent magnets themselves. Even if the arc is not extinguished, the magnetic field surrounding it does not appreciably affect the action of the permanent magnet since the two fields are entirely independent and spaced apart.

Since certain further changes can be made in the foregoing constructions and different embodiments of the invention can be made without departing from the scope thereof, it is intended that all matter shown in the accompanying drawings and described hereinbefore shall be considered as illustrative and not in a limiting sense.

What is claimed as'new is:

1. A circuit interrupter comprising, in combination, means between which an arc is formed resulting in a blast containing particles capable of being influenced by a magnetic field, and magnetic means positioned out of the influence of the magnetic field generated by current flow through said are and along the path of said blast for controlling the movement of a substantial portion of said particles.

2. A circuit interrupter comprising, in combination, means between which an arc is formed resulting in a blast containing particles at high temperature possessingmagnetic properties and supporting combustion on contact with air thereby forming a conducting flame, means confining said blast during a portion of its travel out of proximity with said arc and from contact with the air, and magnetic means for removing a substantial portion of said particles from said blast before the same contact the air thereby substantially preventing the formation of said flame.

so are provided in the spider 11. Four arcu-ately 1: b o sa blast for i flue i .t e ovement A magnetic field. is

the openings in the spi-- thereby substantially preventing the formation of a substantial portion of said particles to move them from said blast.

4. A circuit interrupter comprising, in combination, a pair of terminals between which an arc is formed resulting in a blast containing par-.

ticles possessing magnetic properties at the temperature of the arc and supporting combustion on contact with air thereby forming a conducting of said flame when said blast contacts the air.

9. A fuse comprising, in combination. a pair of terminals interconnected 'by metallic fusible means adapted to be ruptured on flow of predetermined current resulting in an are between said terminals and a blast containing particles of said fusible means that possess magnetic propflame, means directing said blast endwise of said arc is formed resulting in a blast containing par ticles possessing magnetic properties, means directing said blast endwise of said terminals, and

' permanent magnet means providing a magnetic field along the path of said blast for controlling the movement of a substantial portion of said parti'clesto remove them from said blast 6. A circuit interrupter comprising, in combination, a pair of terminals between which an arc is formed resulting in a blast containing metallic particles possessing magnetic properties at the temperature of the arc and supporting combustion on contact with air thereby forming a conducting flame, means directing said blast end wise of said terminals, means confining said blast during a portion of its travel out of proximity with said are and from contact with the air, and permanent magnet means located in the space in which said blast is confined and arranged to permit substantially free movement of the same therethrough and adapted to provide magnetic flux for controlling the movement of a substantial portion of said metallic particles to remove them from said blast thereby leaving substantially none of them therein for contact with the air and preventing the formation of said flame.

7. A fuse comprising, in combination, a pair of terminals interconnected by metallic fusible means adapted to be ruptured on flow of predetermined current resulting in an are between said terminals and a blast containing particles of said fusible means that possess magnetic properties, means directing said blast endwise of said termi-. nals, and means providing a magnetic field independent of the current flow through said are and along the path of said blast for controlling the movement of a substantial portion of said particles to remove them from said blast.

i 8. A fuse comprising, in combination, a pair of terminals interconnected by metallic fusible' means adapted to be ruptured on flow of predetermined current resulting in an are between said terminals and a blast containing particles of said fusible means possessing magnetic properties and supporting combustion on contact with air thereby forming a conducting flame, means directing said blast endwise of said terminals, means confining said blast during a portion of its travel out of proximity with said are and from contact with the air, and means providing a magnetic field independent of the current flow through said are in the space in which said blast is confined for influencing a substantial portion of said particles to remove them from said blast particles frombetween said terminals, and means and supporting combustion on contact with air erties, means directing'said blast endwise of said terminals, and permanent magnet means providing a magnetic field along the path of said blast for influencing a substantial portion of said particles to remove them from; said blast.

10. A fuse comprising, in combination, a pair of terminals interconnected by metallic fusible means adapted to be ruptured on flow of predetermined current rwultlng in an are between said terminals and a blast containing particles of said fusible means possessing magnetic properties and supporting combustion on contact with air there-. by forming a conducting flame, means directing said blast endwise of said terminals, means confining said blast during a portion of its travel out of proximity with said are and from contact with the air,- and permanent magnet means located in the space in which said blast is confined and arranged to permit substantially free movement of the same therethrough and adapted to provide a magnetic field for influencing a substantial portion of said particles to remove them from said blast thereby leaving substantially none of them therein for contact with the air and preventing the formation of said flame.

11. A circuit interrupter comprising, in combination, a pair of relatively movable terminals between which an arc is established resulting in the formation of particles having magnetic properties, arc extinguishing material adapted to evolve an arc extinguishing medium due to the heat of the are, means directing said arc extinguishing medium endwise of said terminals thereby creating a blast which sweeps away said providing a magnetic field independent of the current flow through said are and along the path of said blast for influencing a substantial portion of said particles to remove them from said last.

12. A circuit interrupter comprising, in combination, a pair of relatively movable terminals between which an arc is established resulting in theformation of metallic particles possessing magnetic properties at the temperature of the are thereby forming a conducting flame, arc extinguishing material adapted to evolve an are extinguishing medium due to the heat of the arc, means directing said are extinguishing medium endwise of said terminals thereby creating a blast which sweeps away said metallic particles from between said terminals, means confining said blast out of proximity with said are and from contact with the air, and means providing a magnetic field independent of the current flow through said arc in the space in which said blast resulting in the formation of an are between of the fusible element or elements that possess magnetic properties, are extihguishing material adapted to evolve an arc extinguishing medium due to the heat of the arc, means directing said are extinguishing medium endwise of said terminals thereby creating a blast which sweeps away said metallic particles from between said termi-' nals, and means providing a magnetic field independent of the current flow through said are and along the path of said blast for influencing a sub stantial portion of saidmetallic particles to remove them from said'blast.

14. A fuse comprising, in combination, a pair .of relatively movable terminals interconnected by one or more metallic fusible elements adapted to be blown on flow of predetermined current re-f sulting in the formation of an arc between said terminals accompanied by metallic particles of the fusible element or elements that possess magnetic properties and support combustion on contact with air thereby forming a conducting flame, arc extinguishing material adapted to evolve an arc extinguishing medium due to the heat of. the are, means directing said are extinguishing medium endwise of said terminals p 2,279,631 said terminals accompanied by metallic particles blast is confined for influencing a substantial portion of said particles to remove them from said blast thereby substantially preventing the formation of said flame when said blast contacts the air.

1'7. A fuse comprising, in combination, a pair of relatively movable terminals interconnected by one or more metallic fusible elements adapted to be blown,on fiow of predetermined current resulting in the formation of an arc between said terminals accompanied by metallic particles of the fusible element or elements that possess magnetic properties and support combustion on contact with air thereby forming a conducting flame,

a in which said blast is confined for influencing a thereby creating a blast which sweeps away said metallic particles from between said terminals, means confining said blast during a portion of its travel out of proximity with said are and from contact with the air, and means providing a magnetic field independent of the current flow through said are in the space in which said blast is confined for influencing a substantial portion ofsaid metallic particles to remove them from said blast thereby substantially preventing the formation of said fiame when said blast contacts the air.

' 15. A fuse comprising, in'combination, a pair of terminals interconnected by metallic fusible means adapted to be ruptured on fiow of predetermined current resulting in an are between said terminals and a blast containing particles of said fusible means possessing magnetic properties and supporting combustion on contact with air thereby forming a conducting flame, means directing said blast endwise of said terminals, means confining said blast during a portion of its travel out of proximity with said are and from contact with the air, and a plurality'of permanent magnets in the space in which said blast is confined for influencing a substantial portion of said particles to remove them from saidblast thereby substantially preventing the formation of said flame when said blast contacts the air.

16. A fuse comprising, in combination, a pair of relatively movable terminals interconnected by one or more metallic fusible elements adapted to be blown on flow of predetermined current resulting in the formation of an are between said terminals accompanied by metallic particles of the fusible element or elements thatpossess magnetic properties and support combustion on contact with air thereby forming a conducting flame, arc extinguishing material adapted to evolve an arc extinguishing medium'due to the heat of the are, means directing said arc extinguishing medium endwise of said terminals thereby creating a blast which sweeps away said metallic particles from between said terminals, means confining said blast during a portion of its travel out of proximity with said are and from contact with the air, and a plurality of substantial portion of said metallic particles to remove them from said blast thereby substantially preventing the formation of said flame when v said blast contacts the air.

18. A fuse comprising, in combination, a pair a of relatively movable terminals interconnected by one or more metallic fusible elements adapted'to be blown on flow of predetermined current resulting in the formation of an are between said terminals accompanied by metallic particles of the fusible element or elements that possess magnetic properties and support combustion on contact with air thereby forming a conducting flame, a solid arc extinguishing material adapted to evolve a gaseous arc extinguishing medium due to the heat of the arc, means directing said gaseous arc extinguishing medium endwise of said terminals thereby creating a blast which sweeps away said metallic particles from between said terminals, means confining said blast during a portion of its travel out of proximity with said are and from contact with the air, and means providing a magnetic field independent of the current flow through said are in the space in which said blast is confined for influencing a substanti al portion of said metallic particles to remove them from said blast thereby substantially preventing the formation of said flame when said blast contacts the air.

19. A fuse comprising, in combination, a pairof terminals interconnected by metallic fusible means'adapted to be ruptured on flow of predeof said fusible means possessing magnetic properties and supporting combustion on contact with, air thereby forming a conducting flame, means directing said blast endwise of said terminals,

permanent magnets in the space in which said means confining said blast during a portion of its travel out of proximity with said are and from contact with the air, and aplurality of horseshoe shaped permanent magnets arranged in the space in which said blast is confined so as to permit relatively free flow of the same therethrough for influencing a substantial portion of said particles to remove them from said blast thereby substantiallypreventing the formation of said fiame when said blast contacts the air.

20. A fuse comprising, in combination, a pair of terminals interconnected by metallic fusible means adapted to be ruptured on flow'of predetermined current resulting in an are between said terminals and a blast containing particles of said fusible means possessing magnetic properties and supporting combustion on contact with air thereby forming a conducting flame, means directing said blast endwise of said terminals, means confining said blast during a portion of its travel out of proximity with said are and from contact with the air, and a plurality of arcuately shaped spaced apart permanent magnets located in the space in which said blast is confined so as to permit relatively free flow of the same therethrough for influencing a substantial portion of said particles to remove them from said blast thereby substantially preventing the formation of said flame when said blast contacts the air.

21. A fuse comprising, in combination, a pair of terminals interconnected by metallic fusible means adapted to be ruptured on fiow of predetermined current resulting in an are between saidterminals and a blast containing particles of said fusible means possessing magnetic properties and supporting combustion on contact with air thereby forming a conducting flame, means directing said blast endwise of said terminals, means confining said blast during a portion of its travel out of proximity with said are and from contact with the air, and a plurality of spaced apart coaxial sets of arcuately shaped spaced apart permanent magnets located in the space in which said blast is confined so as to permit relatively free flow of the same therethrough for influencing a substantial portion of said particles to remove them from said blast thereby substantially preventing the formation of said ,fiame when said blast contacts the air.

22. A fuse comprising, in combination, a pair of terminals interconnected 'by metallic fusible means adapted to be ruptured on flow of predetermined current resulting in an are between said terminals and a blast containing particles of said fusible means possessing magnetic properties and supporting combustion on contact with air.thereby forming a conducting flame, means directing said blast endwise of said terminals,

means confining said blast during a portion of its travel out of proximity with said arc and from contact with the air, means directing said blast along a plurality of paths into the space in which it is confined, and means providing a magnetic field along each of said paths for influencing a substantial portion of said particles to remove themfrom said blast thereby substantially preventing the formation of said flame when'said blast contacts the air.

23. A fuse comprising, in combination, a pair of terminals interconnected by metallic fusible means adapted to be ruptured on flow of predetermined current resulting in an arc between said terminals and a blast containing particles of said fusible means possessing magnetic properties and supporting combustion on contact with air thereby forming a conducting flame, means directing said blast endwise of said terminals, means confining said blast during a portion of its travel out of proximity with said are and from contact with the air, means directing said blast along a plurality of paths into the space in which his confined, and a plurality of arcuately shaped circularly arranged spaced apart permanent magnets located in the space in which said blast is confined with the ends thereof along said paths for influencing asubstantial portion of said particles to remove them from said blast thereby substantially preventing the formation of said flame when said blast contacts the air.

24. A circuit interrupter comprising, in combination, means between which an arc is formed resulting in a blast containing particles at high temperature possessing magnetic properties and supporting combustion-on contact with air thereby forming a conducting flame, means confining said blast under pressure, magnetic means for removing a substantial portion of said particles from saidblast while the same is confined under pressure, and means released at a predetermined pressure for allowing said blast to escape to the atmosphere after removal of said particles.

25. A circuit interrupter comprising, in combination, a pair of terminals between which an arc is formed resulting in a blast containing particles possessing magnetic properties, means di recting said blast endwise of said terminals, means confining said blast under pressure, means providing a magnetic field independent of the current flow through said arc for removing a substantial portion of said particles from said blast while the same is confined under pressure, and means released at a predetermined pressure for allowing said blast to escape to the atmosphere after removal of said particles.

GEORGE F. MCMAHON. 

